The present invention relates to nonwoven webs which are detachably adhered to a substrate by the action of electrostatic charges. In one aspect it relates to manipulative articles which are detachably adhered to a substrate by electrostatic forces. Either the manipulative article or substrate is made of an electrostatic nonwoven web. In a specific aspect, the invention relates to a visual display device which has a substrate comprising an electrostatically charged nonwoven fabric whereon informational and/or decorative manipulative articles are adhered for repeated attachment. (For convenience, manipulative articles are simply referred to as manipulatives.) In another specific embodiment, the invention relates to a method for using electrostatically charged nonwoven patterns.
There are a number of display devices which employ manipulatives that may be removably secured to a substrate by hand. These include informational and decorative displays such as bulletin and display boards, design boards for fiber arts such as quilting, toys such as dolls wherein clothing cut-outs are repeatedly attached, and sewing patterns temporarily secured to a fabric for cutting the fabric to a desired shape, to name a few.
As is well known, many bulletin, display, and design boards found in schools, offices, studios, and homes comprise a cork-type board whereon is tacked or pinned a covering of paper or fabric and informational and/or decorative manipulatives are tacked, pinned, or glued onto the paper or fabric cover. There are undesirable aspects to this approach which include holes formed in the manipulative by tacks or pins which after repeated use can cause the manipulative to tatter and eventually render it useless. Holes formed in the paper or fabric covering the board in time can also appear unsightly, requiring the entire cover to be replaced. There are also safety problems associated with using tacks to secure the manipulative in the event a small child may be decorating the display board, as frequently occurs in elementary schools. In the case of using glue to attach a manipulative to the board, it may not be possible to detach the manipulative from the paper or fabric covering for reuse at a later time. The inability to reuse and easily rearrange manipulatives for display and design boards is obviously wasteful in both materials and labor, as can be appreciated from the standpoint of school teachers and designers who arrange and rearrange visual displays with some frequency.
Another use of visual displays is in games and educational aids that use manipulatives detachably secured to a substrate such as magnetic shapes secured to a metal board.
A number of approaches have been taken for detachably securing clothing cut-outs and the like to paper dolls and other playthings. U.S. Pat. No. 3,646,705 discloses a paper doll having a body formed of a stiff paper material whereon a velour sheet is attached using an adhesive, the sheet being cut in the form of an undergarment and adhered to the body at the appropriate location. The exposed surface of the velour sheet is covered by cotton fibers which form nubs. The cotton fibers are held to the velour sheet by electrostatic charges applied to the velour before blowing the cotton fibers onto the velour. An outer garment is cut from a fabric which has a napped side and pressed onto the cotton fibers napped side down. The garment is frictionally secured to the body by the interaction of the cotton fibers and fabric napping. Other publications disclosing methods for frictionally securing a clothing cutout doll body include U.S. Pat. Nos. 2,079,550 and 2,093,207. Other methods for adhering doll clothing have made use of ferromagnetism as evidenced by U.S. Pat. No. 5,178,573. Still another method has been to use the sticking action of polished oil cloth as taught by U.S. Pat. No. 2,331,776. When brought into contact, pieces of the oil cloth will stick together under the action of surface tension in the oil. Each of the above methods requires a significant amount of labor intensive surface preparation to achieve the end result of adhering a manipulative (clothing cut-out) to the substrate (paper doll).
As is well known, in the manufacture of garments and the like, the components of the garment (e.g. sleeve, collar, etc.) are cut from fabric stock and then stitched together. A widely practiced method for cutting the components is to pin a paper pattern of the desired shape to the fabric and then cut around the pattern. A problem in this approach is that after repeated use, the pattern can become tattered from the pins inserted into the pattern. Pinning the pattern to the fabric is also time-consuming. Time-consuming taping or pinning is also required to trace and cut sewing patterns from multi-sized master patterns.
In summary, there are numerous applications for adhering a paper or fabric manipulative to a substrate or backing, it being desirable to achieve this end without tacking, gluing, or pinning the manipulative to the substrate and with minimal surface preparation.
As described in detail below, it has been found efficacious to use electrostatic charges applied to a nonwoven manipulative, a nonwoven substrate, or both for detachable adhering the two together. It further being found efficacious to employ a substrate constructed from an electrostatically charged nonwoven fabric such as a charged meltblown polypropylene fabric. The electrostatic forces are between fabric, paper, and the like, and, unlike prior art magnetic devices, do not involve the use of metallic members.
Nonwoven fabric or web is a fabric made directly from fibers or filaments or from a web of fibers, without the yarn preparation needed for weaving or knitting. The most common nonwovens are meltblown fabrics and spunbonded fabrics. The compositions and methods for manufacturing these well-known fabrics are well known in the art and are described extensively in the literature.
Meltblowing is a method whereby a molten thermoplastic material (e.g. polypropylene) is extruded through a row of closely spaced orifices to form molten or semi-molten fibers. Converging sheets of high velocity air are made to contact the fibers on opposite sides to draw-down the extruded fibers to microsized diameters (viz 0.5-20 microns). The fibers and converging air sheets form a fiber-air stream which is blown onto a rotating collector surface where the fibers deposit in a random way to form a nonwoven fabric. The fabric is held together by inter-fiber entanglement and some inter-fiber sticking while still in the semi-molten state. By varying operating conditions such as polymer throughput, air velocity, and collector speed, meltblown fabrics of different thickness and basis weight (weight per unit surface area) are produced.
Spunbonded fabrics are made by extruding molten thermoplastic polymer to form filaments, drawing the filaments, collecting the drawn filaments to form a web of random filaments, and bonding and/or needlepunching the filaments together. Spunbonded or web fabrics are made from fibers having an average fiber size of 10 to 50 microns.
Meltblown and spunbonded fabrics have good strength, excellent tactile hand, and may be electrostatically charged or uncharged.
Since most meltblown and spunbonded thermoplastics are dialectics, it has been found possible to apply a persistent electrostatic charge to these fabrics. Fabrics so charged are sometimes referred to as electrets, and have been used principally as gas filters where the charges in the electret are very effective in capturing small particles suspended in the gas, which themselves usually carry some electrostatic charge. U.S. Pat. Nos. 4,215,682, and 4,904,174 disclose an apparatus for producing electrets by hot charging and test data illustrating the filtration capabilities of the electret.
PCT application PCT/US/93/09630 discloses cold charging methods and apparatus for applying an electrostatic charge to thermoplastic webs and films.